Congenital heart defects (CHDs) remain the most common type of major birth defects and are the number one cause of death from birth defects during the first year of life. Nearly 40% of them will require one or multiple surgical interventios and accounts for more than 20,000 yearly surgical procedures performed in US alone. During and after surgery, intra-cardiac catheters are used routinely to monitor physiologic parameters, such as intra-cardiac pressure, oxygenation, temperature, pH and lactic acid level, which can change rapidly and may require immediate intervention. While percutaneously inserted catheters, such as Swan-Ganz catheters, have been invaluable in adults, because of size limitation and risks of thrombosis, transthoracic intracardiac catheters have been the standard practice in the neonatal and pediatric populations. Despite the importance and benefits of these intracardiac lines, their maintenance and removal impose risks to the patient. Three major risks for current intra-cardiac line technology are: 1) infection, due to transcutaneous passage of the catheter and communication with unsterile environment; 2) embolization and drug exposure risks inherent in maintaining catheter lumen patency and external repeated manipulations; and 3) bleeding risks from catheter withdrawal. Cardiac tamponade and potential lethal cardiac arrest are clearly the most dreaded and frustrating complications following intracardiac catheter removal. There is a critical need in developing a new technology that allows direct physiologic intracardiac monitoring that carries little or no bleeding and infection risks during the monitorin. We propose to develop Radio-Frequency IDentification (RFID) based wireless sensing system for self-powered implantable sensors determining intracardiac pressure during and after congenital cardiac surgical procedures in children. Our future proposals will focus on oxygen, pH and other sensing technologies. Our research plan includes three major steps: (i) Design and fabrication of miniaturized wireless implantable ultra-thin and highly elastic polyurethane membrane based bioMEMS pressure sensor, (ii) Design and implementation of RFID base wireless sensing system for self-sustainable implanted sensors including: Develop high performance miniaturized implantable antenna; Develop an efficient power scavenging and function control circuits; Develop a low power sensor interface; Integration of sensing system, and (iii) Characterization of the implantable devices through animal studies. While being design-driven, this investigation will answer many fundamental, previously untested questions along the sensor developmental path. By applying novel and highly sensitive pressure sensor design with battery-free concept, a functional, miniaturized, and integrated sensing device will be ready for animal testing during this project. Fulfillment of this project will directly benefit patients with CHD.